Hi Paul, When I wrote the OpenFlight reader I didn't worry to much about the loading times. The focus was on preserving the structure and information of the Flight file. Compared to iterating the list of primitives a couple of times the disk IO is usually dog slow.
Regards, Brede On Sun, Mar 30, 2008 at 2:56 PM, Paul Martz <[EMAIL PROTECTED]> wrote: > > > Gordon, Brede -- Looking for your input on this (but others with FLT > expertise are welcome to chime in as well...) > > Let me explain what the current exporter is doing wrong, and how I believe I > will fix it, and you guys can help me out by looking for flaws or suggesting > alternatives. > > Imagine drawing a highly approximated plane in OSG. You would have a single > Geometry with a single VertexArray containing all vertices, and then several > QUAD_STRIP PrimitiveSets. The result would be a plane approximated by > several quads. > > The exporter currently handles this very inefficiently. For each > PrimitiveSet in the above example, it outputs a Mesh record, followed by a > Local Vertex Pool containing _all_ vertices in the VertexArray, followed by > a Mesh Primitive record for the single QUAD_STRIP. (This was early "turn on" > code written to get some basic functionality in place, which I forgot about. > It was never intended for public consumption.) > > A better implementation would be: Output a Mesh and Local Vertex Pool for > the Geometry object, then a Mesh Primitive for each PrimitiveSet. > > However, this gets complicated if I want to use Face records if the > PrimitiveSet mode is TRIANGLES or QUADS. The code would potentially need to > iterate over the list of PrimitiveSets twice, once processing Mesh record > data, and then once again processing Face record data. > > Alternatively, I could simply not support outputting Face records. A QUAD > becomes a 4-vertex Mesh Primitive of type QuadStrip, and the same concept > for a TRIANGLE. Does this sound feasible? Face records would still be used > for Billboards (not yet implemented) and the Vertex Palette at the top of > the file would really only be needed to store Light Point vertices. > > The downside of this is that if you have multiple Geometry objects that > share the same VertexArray in OSG, you'd get that VertexArray reproduced > multiple times as Local Vertex Pool records in the FLT file; not able to > share that data in the Vertex Palette as you would do when using Face > records. > > Looking forward to your thoughts and input, thanks. > > Paul Martz > Skew Matrix Software LLC > http://www.skew-matrix.com > +1 303 859 9466 > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
